Overland Park staff with a consultant from Benesch launched the floating wetland Wednesday to deter harmful algae from forming in South Lake.

Harmful algae levels in South Lake prompted Overland Park to add a floating wetland that will balance the water body’s ecosystem.

Overland Park public works staff this week launched the floating wetland — a manmade island with native Kansas wetland plants growing on it — to prevent harmful algae from spreading. The island improves the water quality and works by filtering the water, which prevents harmful algae from forming.

Ian Fannin-Hughes, a water quality specialist with Overland Park public works, said South Lake has had problems with harmful algae every year for the past 10 years. The lake is currently listed by Kansas Department of Health and Environment as too harmful for human contact because of the blue-green algae.

“We have decided we need to fix this problem — and the cheapest and probably the most efficient solution we have found — is to put some plants on a buoyant structure and float it out on the lake and soak up some nutrients,” Fannin-Hughes said.

City staff and a consultant from Benesch planted the native plants in the floating wetland and launched it Wednesday onto the surface of the lake. The wetland will remain anchored at the center, with a fence around the edge to deter geese from landing on it.

“It’s made of recycled plastics, so it’s naturally buoyant,” Fannin-Hughes said. Created by Floating Island International, the wetland has holes cut out to make room for native plants, which will eventually push their roots down through the structure.

“If you look at it closely enough, it’s permeable, so the roots can grow through it just like it would naturally grow through the ground,” he said, adding that over time, the wetland will create a more balanced ecosystem in the lake.

South Lake will remain under an algae warning by the Kansas Department of Environment and Health until one of its tests confirms the water is safe.

Eventually, the Kansas Department of Health and Environment will test the waters continually and remove the algae warning signs once the water is safe. Fannin-Hughes said the city should know after the state’s test next week.

The plants on the floating wetlands are all native to Kansas so they can withstand the area’s extreme temperatures and climate. These include blue flag irises, sweet flag flowers, soft rushes and sedge. These plants and the island itself provide a habitat for fish, insects and birds in and around South Lake.

The floating wetlands will remain on South Lake indefinitely, “as long as it’s still doing its job of taking up nutrients, cleaning out pollutants like heavy metals, E coli, and other things that these kind of plants will soak up,” Fannin-Hughes said. “As long as this continues to be a problem with harmful algae in the lake, low oxygen levels, high nutrient levels, we’re going to continue to have this structure out there.”